Accumulated Other Comprehensive Income (Loss) (AOCI balances) (Details 2) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	$ 3,213,416	$ 3,212,840	$ 3,326,796	$ 3,038,854	$ 2,999,536	$ 2,916,782	$ 3,326,796	$ 2,916,782
Other Comprehensive Income (Loss), Net of Tax	21,263	17,068	(37,943)	(18,086)	(12,095)	8,290	388	(21,891)
As of	3,246,658	$ 3,213,416	3,212,840	3,058,911	$ 3,038,854	$ 2,999,536	3,246,658	3,058,911
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of			303,295				303,295
Other comprehensive loss before reclassifications							(2,073)
Net amount reclassified from accumulated other comprehensive income (loss)							2,461
Other Comprehensive Income (Loss), Net of Tax							388
As of	303,683						303,683
Cumulative Foreign Currency Translation Adjustment [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of			(21,888)				(21,888)
Other comprehensive loss before reclassifications							(541)
Net amount reclassified from accumulated other comprehensive income (loss)							0
Other Comprehensive Income (Loss), Net of Tax	20,430			(16,684)			(541)	(17,755)
As of	(22,429)						(22,429)
Unrealized Gain on Pensions and Other Postretirement Plans [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of			325,921				325,921
Other comprehensive loss before reclassifications							0
Net amount reclassified from accumulated other comprehensive income (loss)	712			(1,053)			2,135	(3,463)
Other Comprehensive Income (Loss), Net of Tax	712			(1,053)			2,135	(3,463)
As of	328,056						328,056
Cash Flow Hedges [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of			$ (738)				(738)
Other comprehensive loss before reclassifications							(1,532)
Net amount reclassified from accumulated other comprehensive income (loss)							326
Other Comprehensive Income (Loss), Net of Tax	121			$ (349)			(1,206)	$ (673)
As of	$ (1,944)						$ (1,944)